Long-awaited negotiations between opponents and supporters of the Stuttgart 21 rail renovation project began Friday morning, with some in the strong and vocal opposition saying they were optimistic.

Speaking to reporters before the meeting, Baden-Wuerttemberg State Premier Stefan Mappus said he wanted to make the debate over the project "more transparent."

"We want to show people why we see Stuttgart 21 as an important project for Baden-Wuerttemberg, why it's a project that will last for generations," he said. "We also want to back everything up with facts and move beyond emotions, so that everyone can understand it based on concrete arguments."

Two hours into the discussions, project opponents broke them off to confer with each other before resuming them later in the afternoon. Sources close to the talks said both sides disagreed on the conditions for how to proceed.